Re: Screw magic, We have Science! It works, bitches![3.5][base class][PEACH]
What is this class expected to do before level 5, especially in combat? How exactly does he get the money to afford its creations? Low BaB, low hp, no class features relevant to combat, no spells or maneuvers, no proficiencies (probably an oversight)... unless you expect every engineer to do a lot of professioning, something needs to change.
Give it d6 and medium BaB, and something at level 1 to make the it tolerable to play before you get your toys. Maybe some sort of handcrafted weapon type deal, with special properties but can't be enchanted so it stops being useful eventually. The engineer in TF2 is an able combatant, so it's sort of silly to see him as weak as a kitten (well, weaker) here.
Besides, you get 6+int skill points which is nice, but to actually use your class features you're going to have to put five of them into skills that are really only useful because they feed your class features - even though there are some official classes that do this sort of thing (e.g. truenamer) it isn't good design, and even then they don't do it this much.
Personally, I would give the engineer more plentiful, cheaper (or free altogether), and weaker creations available as he goes up in levels - it's not fun to have to devote most of your budget just so your pet can stay competetive, and if your giant robot goes the way of the dinosaur.
Blueprint: The Boltslinger
Light crossbow modification, requires Engineer 1 and craft(something) X
Suffers no penalty when used with one hand, can be reloaded with same
Blueprint: Eberroneon Hospitality
Melee Weapon modification, requires Engineer 3 and craft(something) x
Struck creatures must make a fortitude save at (10+other factors) or take X bleeding damage for Y rounds
Blueprint: Needed dispenser, here
Engineer Creation, requires Engineer 5 and craft(something) x
All allied creatures within 3 meters gain fast healing 5. This creation is only active for a number of rounds equal to the Engineers class level + int modifier.
And then require maintenance for these things so that you can't just have an adventuring party buy them at a shop, instead needing an actual engineer in the party. So maybe they only last 24 hours before they stop working unless maintained, something like that, or even just make it so only engineers can use them. Or separate them into stronger ones that require intimate knowledge and weaker ones that laypeople can be trained to use. That sort of thing.
Also, there really aren't any weapons for which the "technology" was invented after the 21st century, unless you get very specific. I don't think there are any armies who currently use firearms designed later than the year 2000 (and those are very very similar to much older stuff, too). It's also probably a bad idea to have a capstone based purely on setting and DM fiat.